Confused on sleeping bags ratings and weight

The higher the “fill power” of the down, the less is needed to achieve a given warmth. Thus, everything else being equal, a 900fp bag will be more efficient — and ligher weight — than a 600fp bag. What are you giving up when you buy a high fp, ultra lightweight bag? Moolah — and lots of it!

This REI website has good info. on choosing a sleeping bag:

http://www.rei.com/online/store/LearnShareDetailArticlesList?categoryId=Camping&url=rei/learn/camp/howslbagsf.jsp&vcat=REI_EXPERT_ADVICE_CAMPING

Finally — an important caution! There is no standard for temperature rating. Warmth is subjective. Also, gear makers all assign their own ratings. Many are “optimistic” with their ratings — you may freeze if you take them too literally.

Western Mountaineering, Montbell, Golite — and REI (more or less) — are pretty honest.

While reading and analyzing on your own, you might also want to describe your type of hiking/camping (e.g. car camping or backpacking, three season or four season, etc.), your height and weight, how heavy of a pack you want to lug, and (of course) your budget — and folks will gladly give you their recommendations.

Benjamin hit it on the nose. No need to add more to this.

If you compare one of the lightest bags to a bag that’s a pound heavier but has the same temp rating and is from the same company, these are some things you may notice: The hood is smaller or even missing, there are fewer draft tubes / drawstrings, the zipper extends only halfway down the bag, the bag fits more tightly (and sometimes the ‘regular’ size only fits up to 5’10” instead of 6′), the insulation is lighter (this is fill power), the fabric is lighter (sometimes the weight of the fabric is given in ounces per square foot). I think the weight difference between otherwise identical 800 and 900 fill power bags will be negligible. This thread claims that at least part of the difference between 800 and 900 down is simply the measuring technique used.

I bought a Wicked Fast bag this year and have used it for the season in Europe.The rating is way out.This is not a 0 degrees celcius bag.Check out some European web sites and look for the EN test, comfort figure for the rating you are looking for. Also if you look at the Mammut catalog, i don’t know if they have it on there web site, but they are finding durability problems with 800 and higher loft down.